Re: [Elecraft] Anew k3 owner de ai5os.

[David Woolley]

On 03/05/2024 23:25, Justin Mann wrote:

I notice that the rig has the original 2.8K filter installed, so I’m
thinking that I should add a few more filter to optimize performance


You should first determine whether you are suffering a problem that will 
benefit from this.  XTAL filters will help if you are suffering from 
strong adjacent channel interference, but will degrade the pass band 
flatness, and, probably, the group delay characteristics (pulses will be 
more smeared out).  (I don't know if all the K3 filters are FIR, which 
is needed for ideal group delay behaviour.)



with some different modes.  Were I to add a 250 HZ CW filter would that
also work at 500 HZ?


An ideal 250Hz filter would limit the maximum bandwidth to 250 Hz.  It 
will be even less ideal than the DSP but will dominate the overall 
frequency response outside the 250 Hz (and even near the edges, within 
it).  I'd expect the response to be 10s of dB down before 500 Hz, maybe 
over 60.


--
David Woolley

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Re: [Elecraft] KAT 500 Loses Match

[David Woolley]

The receive part of the penalty, from a lossy antenna, only applies if 
the dominant noise source is after the point of attenuation.  That's not 
generally true at HF.


(I wonder if, at microwave frequencies, it is possible to use 
circulators and isolators to put passive losses in on only the transmit 
path.)


--
David Woolley

On 14/01/2024 05:16, Ken WA8JXM wrote:
Unless its something like a log periodic, I think anything with those 
frequency/SWR specs can only do it with high resistive losses.  It 
reminds me of the HF dipole B makes for the military: it is designed 
to appear to have a low SWR by having 3 db of  resistive losses.  The 
military considered that an acceptable design.   Remember, antenna 
losses affect TX and  RX, so that's 6 db system loss.


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Re: [Elecraft] K2 SSB Power Overshoot on First Syllable

[David Woolley]

This is all, unfortunately, in the proprietary part of the K2, the 
firmware. The K2 doesn't have a gain calibration tables, and I'm not 
sure if it even saves gain settings between transmissions.


With CW it will know that the first transmit level it sees is full 
power, so my guess is that it starts low and builds up to that, but for 
SSB, it won't know when the peak has been reached, so it is going to set 
the transmit gain before it reaches peak and then back it off, but there 
will be a delay in backing it off.  Remember it is primarily a CW 
transmitter.


I would guess, to minimise this, you should set your audio drive levels 
low enough that it gets the correct power open loop.


To make things safe for your amplifier, I guess you would have to add an 
attenuator, so that maximum power will not overdrive the amplifier. 
However, I'm not sure that running at maximum power is good for clean 
signals.


I don't know if there is any open loop control between the power control 
and the transmit gain, or whether it totally relies on closed loop power 
control.  Any open loop control would have to be a compromise, because 
of production spreads in the gain, so, on most instances, would end up 
too high, so as not to limit the maximum output.


I believe there is a gain calibration procedure on the K3 and K4, that 
allows those to make a reasonable open loop power setting at the start 
of a transmission.


--
David Woolley (owner K2 06123)

On 18/12/2023 22:42, Karin Johnson wrote:

Has anyone ever figured out why the Elecraft K2, either base version or with
KPA100 amplifier, has a pronounced
power overshoot on the first syllable using SSB.  I did an internet search
for this problem and did not find
a lot of discussion about it.  Difficult to use an external high power
amplifier as the amplifier may trip on
excessive drive.  My Elecraft K2 works just fine on CW.


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Re: [Elecraft] Noise from KAT500?

[David Woolley]

Most switch mode supplies have transformers. The weight differences 
reflects the difference between a large mass of laminated iron, and a, 
small, ferrite toroid. Using a higher frequency allows a less bulky 
transformer.


--
David Woolley

On 03/12/2023 04:54, David Gilbert wrote:


The ones I measured just a couple of months ago were way too small and 
light to have a transformer in them, and they were horrible.  In any 
case, I recommend that anyone using a wall wart for other than its 
intended equipment (or any standalone new one) be sure to check it for 
both noise and no load voltage regulation.  It's quick and easy to do 
and could save a lot of headaches.


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Re: [Elecraft] [OT] A dumb question about lightning

[David Woolley]

> Lightning can’t tell whether something is grounded
> because the energy pulse hasn’t gotten that far yet.

[Full bottom quote follows reply.]

The path for lightning is determined before the main pulse of energy 
loss happens, and much of the communication involved in determining the 
path happens at the speed of light.


The actual lightning flash is a wave of energy conversion, from 
electrostatic, to heat (and then to sound and light).  The energy to 
drive it is already there.  It is isn't travelling down the growing 
bolt, but rather being taken from the volume surrounding it.


In fact, the main energy conversion doesn't happen until after the 
complete initial path has been established and actually propagates upwards.


Where it happens will be influenced by the distance between grounded 
conductors and the cloud, so, at the early stages, the presence of 
grounds (although not necessarily particularly good ones) will have an 
impact. However, it will also depend on the degree of corona discharge, 
which will depend on the sharpness of objects, as corona discharges 
will, effectively extend the effect of the ground into the air above the 
point.


The whole process will be complicated, and there will be a significant 
random element, but the presence of grounded conductors will have an 
effect in the very early stages.


--
David Woolley

On 28/07/2023 22:46, Walter Underwood wrote:

Lightning can’t tell whether something is grounded because the energy pulse 
hasn’t gotten that far yet.

Lightning induces a current in every nearby conductor. When that pulse of 
current reaches a building or electronics, we want to provide a low impedance 
path to a safe sink (ground rods) and a high impedance path to the equipment (a 
choke). A lightning arrestor is a temporary low impedance path to ground for 
conductors that aren’t normally grounded.

The best high impedance path is disconnecting your equipment. That won’t stop a 
direct strike, because that will induce currents in the disconnected equipment. 
But it will help almost all the time.




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Re: [Elecraft] Where to put the wattmeter

[David Woolley]

I'm fairly sure that (forward power) - (reverse power) gives the correct 
nett output power, before cable and antenna losses.   I'd need to review 
the maths to be sure.  Most reflected power ends up re-re-reflected, as 
additional forward power.  A high SWR will giver reflected power almost 
as high as forward power.


--
David Wooley

On 13/04/2023 18:20, Bob McGraw wrote:
Case and point.   On one of my antennas, on a frequency where the SWR is 
high, the FWD power indicated on the external meter is 200 watts.  No 
way the radio is producing 200 watts.  At the antenna matched frequency 
the external meter indicates 100 watts.


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Re: [Elecraft] KX3 and SWR

[David Woolley]

It's not actually SWR that kills PAs, but rather the resulting 
over-voltage or over-current.  With an open circuit load, the risk would 
be mainly over-voltage, but whilst that would be a problem with a class 
C PA, I'm not so sure that there is a big risk from class AB, push-pull, 
ones.


A PA might survive a very high SWR for some loads, but be very fussy for 
other ones.


--
David Woolley

On 16/03/2023 15:58, Ingo Meyer DK3RED wrote:
The KX3 should tolerate an SWR of 1.6:1. I have already unintentionally 
transmitted with my KX3 (5W CW) without antenna and the KX3 is still in 
good health. The manual says at page 6: "The KX3 reduces power if SWR is 
high."




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Re: [Elecraft] Win4K3 - Virtual COM Ports on Windows 10

[David Woolley]

Having been involved on the periphery of other software certification 
processes, I suspect that getting a driver Microsoft approved is an 
expensive process, both in terms of fees to Microsoft, and internal 
staff time.


I think it is unlikely that you will get an approved driver which is not 
backed by large hardware sales to fund this process.


Any approval is likely to be for a single version, not for the open 
source project as a whole.


--
David Woolley

On 15/01/2023 15:27, John Overbaugh wrote:

I'm trying to set up my KX3 on a new Windows 10 computer using Win4K3.
Has anyone found a satisfactory solution to com0com's test driver
issue? Windows 10 enforces signed drivers; because com0com is a test
driver Windows doesn't trust it. I don't want to disable secure boot
and allow unsigned drivers, so the work-around isn't acceptable to me.

Has anyone found a driver they like which creates virtual com ports?

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Re: [Elecraft] KPA1500 Faulting for High SWR inappropriately

[David Woolley]

On 20/12/2022 01:38, Bob McGraw wrote:
Use an antenna analyzer to determine the actual complex antenna 
impedance.   I've always viewed SWR as more of a hocus pocus value, easy 
value to obtain, but very broad in definition as it is a ratio between 
two impedance, both usually unknown.


Whilst I'd agree that its usefulness is overstated, it is not the ratio 
of two impedances, and one of the impedances is generally known (unless 
you are measuring the the Lecher line way, by actually finding the 
voltage peaks and troughs on an open line, of unknown characteristic 
impedance).


I don't think the professionals have used for a very long time.  They 
prefer s parameters, or if they want a single number, they use return 
loss.  It is basically only heavily used in the amateur and CB communities.


Generally it is defined assuming an ideal transmission line, with a 
purely resistive impedance. and in that case, the only time that it 
equals a ratio is when the load impedance is also purely resistive.


The main advantage of SWR is that it can be physically measured without 
having to use anything other than the magnitude of the voltages read 
(i.e. no phase information).  But this means that the same SWR can be 
completely safe or destroy a PA, depending on the phase information.


--
David Woolley
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Re: [Elecraft] [K2] CAL-PLL Question

[David Woolley]

The only reason I can think of why this might apply is if the grounding 
of the bottom cover was poor.  Whilst it certainly can be poor, because 
of paint not having been properly masked around the mounting blocks, and 
I recommend cleaning all paint off, around them, I'd be surprised if 
enough of the induced currents, in the bottom panel, flowed through 
these points to make a difference.


--
David Woolley
Owner K2 06123

On 30/07/2022 16:25, Wolfgang wrote:


in a german QRP forum I found this hint from Peter, DL2FI (SK).


    In any case, the PLL calibration must be redone whenever the bottom 
cover of the K2 has been opened.


Therefore my question, of it is really so that "CAL-PLL" must be done 
again after *each opening* of the lower housing cover?




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Re: [Elecraft] Using the Antenna Tuner in the XPA100

[David Woolley]

Being automatic doesn't constrain the network topology or 
implementation; you could add servos and a controller to the 180s-1. 
However, most typical automated tuners are L networks, and differ from 
the aircraft one described in using switched combinations of fixed 
inductors and fixed capacitors, which means they have a finite number of 
settings.  The Elecraft ones cover wide range of values (256 equally 
spaced inductance values and 256 equally spaced capacitance ones), but 
some built into other transceivers have a limited range.


In circumstances that require a load end capacitor, the Elecraft type 
design reverses the L network, rather than converting to a Pi topology.


All L (and Pi) networks, are designed to feed unbalanced loads fed 
against the same ground reference as at the transmitter output.  If 
possible, they should be at the antenna end of the feeder, so should not 
be driving a feeder themselves.


You don't need a tuner when driving a matched line and an unmatched line 
can present a very wide range of impedances.


Actually, looking at the circuit of the 180S-1, in 
<http://collinsradio.org/archives/manuals/180S-1_2nd-ed-02-62_.pdf>, the 
transmitter side capacitor topology is a hybrid of a pure variable 
capacitor and the switched lumped capacitors that are used for all the 
capacitors in the Elecraft type designs, although they only provide for 
two fixed values, in addition to zero, from two switches (500 and 
1,000), whereas the Elecraft type design would give 500, 1,000, and 
1,500.  I guess capacitors were expensive.

--
David Woolley


On 02/07/2022 23:13, Mister Mike wrote:

The 180S-1 consists of an L network which is formed by a variable air-capacitor on the 
input, and a variable roller inductor as the series coil.  It is then possible to expand 
this network (by means of a jumper) with a vacuum capacitor on the output of the 
"PI", in cases where the tuning solution would call for this.  The vacuum 
variable capacitor can be either shunted on the output, or placed in series with the 
inductor. This configuration allows for virtually every kind of antenna to be tuned.

The “automatic” antenna tuner is a completely new concept for me.  They appear to 
be designed to tune unbalanced coaxial feedlines and not an end-fed wire.   I have 
one in my K3 but prefer to use the 180S-1 or my B VS1500A which is a 
“transmatch” based on the design by Doug DeMaw, W1CER/W1FB SK in the 1960s.



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Re: [Elecraft] I need a Sherlock Holmes (weird spurs on 40m)

[David Woolley]

OFDM is also what is used for [A]DSL, and, but at UHF, or SHF, digital 
TV (terrestrial and satellite).  It's also, at least in Europe, for 
digital radio, at VHF.  I think it is also used for 4/5G mobile. phones.


It is not intrinsically secure.  It's main advantage is that it gets 
close to the theoretical (Shannon) limits on error free bit rates in the 
presence of purely Gaussian noise, and has good multipath tolerance (not 
useful for ADSL, though).


Encryption isn't required.  Scrambling may be done to avoid spectral 
peaks, but actually encryption, if used, is done at a higher level.


--
David Woolley


On 08/06/2022 09:22, Dynolab wrote:

Your 24kHz spaced spurs from 6.6 MHz to 7.4MHz sounds very much like Orthogonal 
Frequency Division Multiplexing (OFDM).
A secure type of modulation encryption that is often used on the HF bands for 
High Frequency securities trading.
If it is a foreign source, they may not respect our 40 meter ham band 
frequencies.

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Re: [Elecraft] Troubleshooting KIO2

[David Woolley]

It's going to be similar to the application circuit in section 7.1 of 
<https://ftdichip.com/wp-content/uploads/2020/08/DS_FT232R.pdf>, except 
that not all the wires may be connected, and, in particular, any that 
conflict with the K2's use of a pin on the connector for Auxbus won't be 
connected.  (The KIO2 documentation will tell you which pins are 
actually used in a standard way.)


It's just possible that they have left out the level convertors, as it 
would probably work without them.


Assuming it has the level convertors, the standard tool for looking at 
what is happening will be something like this: 
<https://czh-labs.com/products/czh-labs-rs232-led-link-tester-module-db9-male-to-db9-female> 
(picked at random from a Google search.  If it doesn't have level 
convertors, the LEDs may only light up for one state, of the nominally 
bipolar signal.  (If auxbus is on one of the monitored pins, it might be 
disrupted, but the resistor on the LED should ensure that there is no 
permanent damage.  It would be better to do it on the end of the 
official KIO2 to RS232 cable, though.


Incidentally the S in USB stands for serial, but it is different, and 
much more complex, serial protocol.


Also, I found the price eye watering, given what is probably in it; the 
problem with very low production run products.  Things like Arduino 
throw in all but the level convertors and DB9 connectors, as just part 
of something that sells for under GBP 10, although current Arduinos use 
an AtMega microcontroller chip, rather than the FTDI chip.


Before considering alternatives, do beware of the the vulnerable, 
Auxbus, signal on the non-standard K2 connector.


My PC motherboard was selected because it had a real RS232C asynchronous 
port.


--
David Woolley
Owner K2 06123

On 27/05/2022 20:41, Dave Sublette wrote:

It would be nice to have a schematic of the KUSB cable.

If anyone has experience troubleshooting this sort of thing or knows where
to get more information, please let me know.


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Re: [Elecraft] K3 and Kenwood MC-50 mike

[David Woolley]

The purpose of the transformer isn't to get anything close to a 
conjugate match.  Doing so would produce a very inefficient PA, and, I 
suspect, would produce unacceptable levels of distortion 
(non-linearities in the output impedance would be visible in the signal).


The purpose is reduce the design load seen by the PA to a point where 
the design power is achievable with the available power supply voltage.


The design load is determined by P = a * V^2/R, where a is a constant to 
allow for things like not being able to actually reach +/- V, RMS 
correction, the output impedance not being truly zero, and a safety 
margin, to allow for the presented R not being no higher than the design 
value (SWR not 1:1, with load on the high side).  I'm assuming the 
reactive part is being tuned out.


For an ideal, class B, PA, with zero output impedance, and full rail 
swing, and no safety margin, a would, I believe, be 0.5.  I don't know 
what the actual design rule value is, for typical, real world, designs.


You can see this in the alternative winding configuration for the K2, to 
give more efficiency at reduce power.  That increases the presented 
load, but doesn't change the effective output impedance.


--
David Woolley

On 11/04/2022 16:37, Joe Subich, W4TV wrote:




On 2022-04-11 10:55 AM, David Woolley wrote:

RF PAs are also, typically, much lower impedance than their design load.




Except they *DO HAVE* impedance matching - typically a broadband output
transformer (4:1, 9:1, 16:1) to 'get close' followed by some kind of
"antenna tuner" (automatic or manual), i.e. matching network to match
the working load.


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Re: [Elecraft] K3 and Kenwood MC-50 mike

[David Woolley]

RF PAs are also, typically, much lower impedance than their design load.

--
David Woolley

On 09/04/2022 18:23, Jim Brown wrote:


RF impedances ARE matched. Audio impedances are NOT. Low-Z out, high Z in.


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Re: [Elecraft] KPA500 Issue

[David Woolley]

Key clicks don't require non-linearity.  They are the result of 
modulating with a signal that has an infinite bandwidth, because of the 
sharp transitions at leading and trailing edges.  That results in 
infinite side bands.  (Actually any signal that communicates information 
in finite time will have infinite side bands, but by correct shaping you 
can make them very small.)


--
David Woolley
Owner K2 06123.


On 01/04/2022 23:06, Jim Brown wrote:

On 4/1/2022 2:35 PM, kevin wrote:

It is more accurately referenced as Discontinuous Wave.


Actually, it is 100% amplitude modulation of a carrier by a rectangular 
wave train. That modulation excites non-linearity in the transmitter 
signal chain and produce intermodulation distortion that is heard as 
clicks.



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Re: [Elecraft] K2 advice needed - what to buy

[David Woolley]

With such an out of balance antenna, the case, power supply and leads of 
the transmitter are all going to be parts of the real antenna.  I'm not 
sure, therefore, that  you can rely on an SWR measurement made using 
other equipment.


You should certainly make sure that paint is removed from inside the 
panels around where the 2-d fasteners go, to maximise the RF integrity 
of the outside of the case.  As you are not using a microphone, you 
probably don't need to bond signal ground to the case there, as well 
<https://ftp.elecraft.com/K2/Mod%20Notes%20Alerts/Grounding%20the%20K2%20Mic%20Jack.pdf>.


PS.  Starting a subject with Re, when it is not a reply, will be scored 
as possible spam by some spam filters.


--
David Woolley
Owner K2 06123

On 23/11/2021 11:57, E J Martin wrote:

I have a long wire resonant (SWR < 1.4) across the 40 band hence don't need an 
ATU.


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Re: [Elecraft] Headphones for Hearing Loss

[David Woolley]

I'm not sure that boosting high frequencies (assuming you have simple, 
age related, type losses) is really a safe thing to do.  Whilst hearing 
aids do this, they also apply dynamic range compression, to minimise the 
additional hearing damage caused by the aid for loud sources.


Incidentally, the standard correction applied by hearing aids is 
approximately half the number of dB's of loss.  They don't try to fully 
cancel the loss.


--
David Woolley

On 14/10/2021 00:24, Jim Brown wrote:


First, one that works for K6DGW, who mostly works CW and has a lot of 
hearing loss. Set RXEQ with maximum cut for the 3 lowest bands (50, 100, 
200) and cut at least 6 dB on the 4th (400 Hz). Set the highest bands 
for max boost. Depending on what note you like for CW, play with the 400 
Hz band.


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Re: [Elecraft] K2/100 RS232 trouble

[David Woolley]

The problem of using a standard cable with the serial port is not that 
it might fail to operate as a serial port, but rather than it might 
permanently destroy the (non-RS232) internal signalling within the 
transceiver.


If that signalling is destroyed, the set won't be able to do anything 
useful, so won't be able to operate the serial port.


In fact there seem to be two pins that are used for signals that cannot 
tolerate RS232 voltages.


This is only a may, because it depends on which wires in the cable are 
actually connected at the other end.  The special cable basically leaves 
some pins unconnected.


--
David Woolley
Owner K2 06123
On 10/09/2021 13:12, Andy McMullin wrote:

You are using the special RS232 cable aren’t you? You must connect with a cable 
matching the special pinout first. If you try a straight connection it will 
fail.



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Re: [Elecraft] I Keep Getting Kicked Out

[David Woolley]

You need to reduce the sensitivity of your spam checker, or white list 
mail with an envelope sender of elecraft-boun...@mailman.qth.net.


Or, if you mailbox is overflowing, you need to clear it more often, so 
mail doesn't get rejected because it is too full.


It is just possible that receiving in digest may help, e.g. by diluting 
the parts that cause the false positives in the spam checker.  It is 
also possible that the spam checker doesn't like some contributor's 
domains, and, with some luck, these will not be seen, because they are 
not in the main email headers in a digest.


Nearly all the spam detections, I see for the list, are false positives. 
I take it in MIME digest format, however, sometimes posts from 
legitimate members get forged onto the list.

--
David Woolley

On 23/07/2021 01:51, kg6mzs wrote:

I keep getting kicked off the reflector for the stated reason of too 
many bounces.  How come no other list seems to have this problem?


I'd love to stay subscribed to the list but re-applying is becoming too 
onerous.


Is there anything we can do to remedy this problem?




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Re: [Elecraft] The next generation KAT500

[David Woolley]

That basically requires measuring I and Q components from the reflected 
power coupler, rather than just magnitude.  That, in turn, means 
deriving a reasonably accurate quadrature copy of the main transmit 
signal.  I suspect one of the factors here may be that the tuner has a 
wider matching range than the dynamic range of the reflected power sensor.


However, even with the existing hardware, if you are in the dynamic 
range of the reflected power coupler, you can work out which constant 
SWR circle you are on on the Smith chart, and I suspect that, if you 
probed with carefully chosen partial corrections you could probably find 
two solutions with one more measurement, and remove the ambiguity with 
the third, even using the existing hardware.  The third could probably 
be based on one of the two solutions.


I'd still suggest the biggest problem is the dynamic range of the 
reverse coupler, as, once you have an in range SWR, you can use a 
minimum finding algorithm to home in.


Incidentally, if you do need to do a brute force search, using a Gray 
code progression will be kinder on the relays than linear sweeps.


Some of this may actually already be being done.
--
David Woolley


On 09/07/2021 00:34, Andy Durbin wrote:

The next generation KAT500 should measure the complex load impedance, including 
the sign of X, compute the L and C required to match, and plug in those values 
as the initial tuning solution.  Why wouldn't this approach be better than 
flailing around in the dark like most auto tuners seem to do?

I doubt this will ever happen but the idea of combining the KAT500, LP-100A, and an 
Arduino controller to implement this "smart" tuner keeps banging around in my 
head.   Maybe one day I'll give it a try.

73,
Andy, k3wyc





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Re: [Elecraft] Generic words on temperature

[David Woolley]

100°F is well within the survivable body core temperature range, so it 
should never trigger pain receptors.


In fact, I believe it was defined based on the nominal core body 
temperature of a cow.


Did you mean 100°C?

--
David Woolley


On 04/07/2021 00:03, Francis Belliveau wrote:

Another rule of thumb for those who care.

When you hold a finger on something and it is 10 seconds to pain threshold, 
that location is about 100 degrees F.
This is not an absolute constant, but I have checked it a few times since I was 
told that, and it seems to be true for me.



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Re: [Elecraft] Temperature or Warmth of KPA500 when "Off" ?

[David Woolley]

I don't think this design would be acceptable in modern consumer 
equipment, at least not in Europe. Typically they would have an 
auxiliary power supply for the microcontroller, to reduce power 
consumption to well under 1 watt, and maintain a reasonably good power 
factor, when in a soft power off state.


Current and voltage figures quoted elsewhere in the thread suggest over 
10 watts and an unknown number of VA.  There was a lot of campaigning to 
hard power off devices at a time when standby powers were more like 5 watts.


On 01/07/2021 00:09, Jack Brindle wrote:


It is powered by the 5V linear regulator, which is providing the heat you feel, 
along with the +12V and -12V regulators (also linear). I seem to recall that 
the input to the regulator is something like +15 or +18V, which gets regulated 
down to the three supplies that are used for running the microcontroller the 
RS-232 interfaces and the LCD. The LCD is disabled when front-power is off.

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Re: [Elecraft] Roofing filters and DSP bandwidth tuning

[David Woolley]

On 27/01/2021 20:35, Fred Jensen wrote:
   It follows that you'd probably like the selection of roofing filters 
to follow the DSP BW as closely as possible.


Having the roofing filter too close to the DSP filter is not necessarily 
a good thing, as the roofing filters are likely to have worse passband 
ripples and will have non-linear phase responses, which can compromise 
digital modes.  At least some of the DSP filters are finite impulse 
response, meaning they are also linear phase, which means that pulses 
will not get smeared out.


--
David Woolley

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Re: [Elecraft] Headphones for Hearing Loss

[David Woolley]

Firstly, nothing above about 3.4kHz is relevant for communications, and 
for typical SSB that is down to about 2.7 to 3kHz.


However, with a large hearing loss, you really need to find a solution 
that uses the hearing aids, as digital aids will have safety features 
and dynamic range compression that will minimise further damage to your 
hearing.


You didn't mention which style you had.  Whilst open fit would be common 
for people with good low frequency responses, I'm not sure that they 
would be used with that level of loss.  I have full moulds, because I 
have an atypical loss in one ear, so I'm not sure of the limitations of 
open fit, but as they normally bypass the low frequencies, they may be 
unsuitable for a direct audio feed.


I'm not sure to what extent that also applies to receiver in the canal.

I suspect the direct bypass means they are less stable against feedback.

For full moulds, and over the ear, I think you would normally get the 
options of electrical connections to audio shoes, induction loop, 
bluetooth (and 3.5mm audio) adapters that you wear on the body and send 
a very short range transmission to the actual aids.  Some aids would 
directly support bluetooth.


Incidentally, it may well not be well known, but hearing aid 
prescriptions generally under-compensate by about a factor of two in the 
dB values, so an aid for a 60dB loss would, typically, only have 30dB 
gain at the frequency in question.


--
David Woolley

On 26/01/2021 16:22, Joseph Shuman wrote:

I have severe high-frequency hearing loss, up to 85 dB at 6-8KHz and 60 dB at 
3-4KHz.  Lower than that my hearing is close to normal for my age.  I use hearing 
aids and the style I have won’t work with headphones.  I have the equalizer on the 
KX2 set to boost the highs, OK with an external amp & speaker but it is not 
enough with the headphones I have.  Any experience/recommendations with headphones 
that have a built-in equalizer or treble boost?  SSB operator.  (KX2 #3007, KXPA100 
#2802)



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Re: [Elecraft] [K4] IF Out

[David Woolley]

The K4 doesn't have an IF, so it can't have an IF output!  Did you mean 
the K4D, although, admittedly, it might use the same box?


--
David Woolley


On 21/01/2021 00:45, john wrote:
The K4 does not appear to have an IF Out connector on the rear panel, 
like the K3. Can the XVTR IF Out be configured to provide this 
functionality?


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Re: [Elecraft] Arecibo antenna collapses

[David Woolley]

Arecibo was steerable by moving the feed point.  They compensated for 
spherical aberration by using a travelling wave antenna for the feed, 
and later by using a series of sub-reflectors, the latter in the 
gondola.  The spherical aberration is independent of pointing direction, 
which, I believe, is why they went for a spherical, rather than a 
parabolic, shape.


--
David Woolley


On 02/12/2020 17:22, Andrew Faber wrote:

So by moving the cabin and pulling on cables, they can apparently track through 
about 20 degrees, unlike Arecibo, which is fixed in a spherical shape.


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Re: [Elecraft] Firmware development

[David Woolley]

My impression is that all hobbyist fused filament printer use open 
source firmware.  The difference is likely to be whether the vendor 
pre-configures and pre-installs it.  That probably applies to all fused 
filament printers.


I think the original movement behind these was that you could, largely, 
use the printer to make the printer, so they attracted people who wanted 
to flash their own firmware.


--
David Woolley

On 27/11/2020 04:26, SteveL wrote:

I own a popular open-source based 3D printer.  Finding the firmware to run the 
printer reliably is a challenge.  Once found (or so I thought) then there’s the task 
of compiling and loading the firmware after customizing specifically for one of 4 
different mother boards the vendor shipped with the same printer model, using vague 
and incomplete recommendations from the “community".  Then there’s



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Re: [Elecraft] k2 spurious

[David Woolley]

Surely the binocular transformer is converting the input impedance of 
the filter to the optimum load line for the PA transistors.  Typically 
that would mean such that the the voltage swing was just short of the 
full supply rail for the worst case complex impedance, at the worst case 
acceptable SWR, for maximum power, and with that power.


Also that transformer provides negative feedback.

I'd expect the actual PA collector impedance to be a lot higher than the 
impedance reflected through the transformer, as transistors and FETs 
are, to a first approximation, current sources, although the negative 
feedback would actually make the reverse termination impedance much 
lower than that from the transformer.


A hint that is the case is the option for different winding ratio if you 
are always going to use a lower maximum power.  Maximising the voltage 
swing increases the efficiency.  The alternative ratio doesn't transform 
the filter input impedance down so much.


I mention this as there is a common misconception that the "maximum 
power transfer theorem" actually applies in such cases, when applying it 
would produce less than 50% efficiency.


--
David Woolley
Owner K2 06123


On 25/10/2020 18:17, Don Wilhelm wrote:


The binocular toroid is a transformer to match the impedance of the PA 
collectors to 50 ohms, which is the input impedance of the Low Pass 
Filters.


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Re: [Elecraft] Smoke detectors

[David Woolley]

Radio waves are non-ionising radiation, so there is no fundamental 
reason why radio frequencies should trigger ionisation detectors.


Also, at least in Europe, ionisation detectors are no longer the 
preferred type. Optical detectors are the generally preferred type, and 
ones which combine heat and optical detection seem to be most favoured.


Actually ionisation detectors alarm when the current reduces, so 
additional ionisation would probably de-sensitise, rather than trigger 
them.  They include an alpha emitter to generate the ionisation, so are 
radioactive.


The main advantage is that they are cheap.

--
David Woolley

On 25/10/2020 10:36, Geoffrey Feldman wrote:

The reason to keep smoke detectors from Amateur Radios is that they detect
smoke by ionization from a radioactive source.  A strong near field will set
them off.  The good news is that this is your indication that all is not > right at the feed line (Or the antenna is unhealthy close).  I have 

had this

experience myself, fixed the feed line and the issue went away.   That was
with 100w on 80 meters.  Unlike real smoke, the detector will stop
complaining when the transmission stops.

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Re: [Elecraft] K3, k4 Black knobs

[David Woolley]

Red is used because the rod cells, that are used for night vision, down 
to a point where they are almost quantum limited 
<https://www.cns.nyu.edu/csh/csh04/Articles/Rieke1998.pdf>, have a peak 
sensitivity for greenish blue, but are very insensitive to very deep 
reds, whilst they retain some sensitivity to the high frequency limit of 
the blue cone cells.  Night vision doesn't have the same spectral 
response as a monochrome camera.


Light of a colour to which they are sensitive bleaches the sensor 
pigment, reducing sensitivity.


Ideally, you don't want to use the brightest red LEDs, but rather those 
with the longest wavelength consistent with an adequate remaining cone 
cell sensitivity.


See <https://midimagic.sgc-hosting.com/huvision.htm> for typical colour 
sensitivity curves.


--
David Woolley

On 16/10/2020 14:31, Ken B wrote:

Why do you use red  and not blue or green



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Re: [Elecraft] K4 sound card capability

[David Woolley]

As there is not even a block diagram published, I don't know the answer, 
but ideally one would not want baseband analogue audio anywhere in the 
path, so one would not want a sound card, integrated or not, but rather 
direct access to a digital feed from the DSP.



On 04/10/2020 20:07, Terry Brown wrote:

I assume the K4 has an internal sound card to take the place of the signalink


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Re: [Elecraft] New KX3 reverse voltage smoke

[David Woolley]

See page 3 of 
 
for confirmation that the KX3 chassis is connected to the the same 
network as the negative supply to the internal components.


On 05/09/2020 19:32, Alan - G4GNX wrote:
I'd be very surprised if Elecraft had connected the negative supply to 
chassis ground inside the KX3 either.


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Re: [Elecraft] New KX3 reverse voltage smoke

[David Woolley]

I'd definitely expect the chassis ground to have a low impedance 
connection to the negative power supply rail, and normally that would be 
a DC connection.  Without it the screening of internal circuitry would 
be less effective.


The K2 definitely has a DC path from supply negative to the case.

I'd also expect any power supply large enough to require a ground 
connection, and eventually have exposed voltage output rails, to have 
ground connected to one.  Without that, capacitive leakage can generate 
a significant electric shock hazard, or even cause damage when the 
powered equipment is being interconnected with equipment on another 
power supply.


If the safety earth rises significantly above that of other conducting 
items during a fault, there is a defect in earth bonding in the 
installation as a whole, that needs urgent rectification.


--
David Woolley
Owner K2 06123.

On 05/09/2020 19:32, Alan - G4GNX wrote:
I don't understand why the antenna being connected provided a path to 
ground for the supply.


If that really is the case, there would seem to be a fault with your 
power supply. The secondary (low voltage) side of a PSU should never be 
connected to ground. Both poles should always 'float'.


I'd be very surprised if Elecraft had connected the negative supply to 
chassis ground inside the KX3 either.


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Re: [Elecraft] W1 Programming???

[David Woolley]

When you are interacting with a USB thumb drive, you are normally 
interacting with a USB mass storage class device, not with raw USB. 
Most cheap USB boltons to hardware are done with the communications 
class, and emulate an asynchronous serial port (although some may use 
the human interface device (mouse/keyboard) class.


As such, the ability to write code for the thumb drive doesn't mean you 
can use the same code on the wattmeter, even though the chances are that 
the USB side can be treated as though it were something else.


--
David Woolley
Owner K2 06123.

On 05/09/2020 01:57, kevinr wrote:
I just wrote a little code using Posix standards under Ubuntu with g++ 
for my compiler.  Looks like USB is treated as a normal stream of 
characters.  The most difficult part was finding my USB thumb drive in 
the file system.



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Re: [Elecraft] K2 transmit limitations

[David Woolley]

I don't believe there is any ability to frequency restrict the K2.  It's 
essentially a bag of components, and  most countries allow licensed 
amateurs to home construct from components, and applying hard limits in 
such cases would be difficult.


On 09/08/2020 08:29, Ingo Meyer, DK3RED wrote:
Yes, it is possible with a K2. But I don't know any reason why a ham 
radio operator should send outside the frequencies that are reserved for 
us.


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Re: [Elecraft] Matching resonant antennas

[David Woolley]

You can only have a 1:1 SWR at a single impedance.  If the design 
impedance is purely resistive, that means you can only have 1:1 for a 
resistive and therefore on-resonance load (or one that can be treated as 
having no reactive behaviour at the frequencies of interest - e.g. an 
ideal dummy load).


On 15/07/2020 20:30, Ken WA8JXM wrote:

Conversely, a non-resonant antenna can have a 1:1 SWR.


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Re: [Elecraft] Copying CW at high speeds

[David Woolley]

Neve conduction is actually a mixture of chemical and electrical 
mechanisms, in vertebrates.  The signal travels electrically in short 
hops, and is then regenerated by a chemical process.  Invertebrates have 
propagation velocities of more like 1 metre / second. 
<http://www.biologymad.com/NervousSystem/nerveimpulses.htm#impulsespeed>


--
David Woolley

On 29/12/2019 03:27, Kevin McQuiggin wrote:

It does not negate the argument, but nerve impulses are based on chemical 
reactions in neurons, and only travel at about 120 metres per second.


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Re: [Elecraft] Dual panadapter on K4 at Pacificon

[David Woolley]

There is something wrong if you have to re-run a Windows installer every 
time that you boot Windows!  The Meinberg product is just an installer; 
the actual software installed is the open source NTP reference 
implementation, currently owned by the University of Delaware, and 
developed under the leadership of David Mills W3HCF.


The reference version means the version used to verify the 
implementability of the specification in the RFC document.


--
David Woolley
Owner K2 06123



On 18/10/2019 23:31, David Gilbert wrote:
Agree about Windows.  When I power on my Win10 laptop that I use for FT8 
the damn thing is about 2.5 seconds off until Meinberg decides to step 
in and fix things.  Pretty sad.





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Re: [Elecraft] test

[David Woolley]

The longer established email programs that support HTML mail will always 
send it as multipart/alternative, with both HTML and plain text 
versions.  Almost certainly your email program does that.  However, it 
appears that there are an increasing number of email programs that only 
send HTML or other rich text versions.


I think the list software is stripping out the text/html variant, rather 
than rendering the HTML as plain text.



--
David Woolley

On 23/07/2019 18:51, RALPH TURK wrote:


This is a test of   HTML



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Re: [Elecraft] OT a bit: K3 Ant Tuner

[David Woolley]

I think we have the maximum power transfer theorem fallacy again here. 
The maximum power transfer theorem does not give the right result when 
you want to maximise efficiency, which is what you generally want to do 
in a transmitter, as it always results in worse than 50% efficiency.


One would expect the output impedance of transmitter to not only differ 
from 50 ohms but to radically differ from it.  If I remember correctly 
for a simple transconductance device, the resistive component will be 
many times 50 ohms.  If heavy negative feedback is used, I think it may 
actually be much lower than the "matched" value.  See 
<https://www.edn.com/Pdf/ViewPdf?contentItemId=4124437> for typical real 
reverse termination impedances.


Unless you put a (ferrite) isolator between transmitter and filter your 
filter design needs to assume far from 50 ohm reverse termination.


Putting a matching network in will simply destroy the PA efficiency, or 
even destroy the PA, through overheating.  If one really wanted to do 
it, you would have to adjust the SWR based on a received signal.


That matching network, will, itself, have a frequency response, as will 
the one leading to antenna.


Another reason for not operating anywhere near 50 ohm reverse terminated 
is that the dynamic resistance of output devices is far from linear, and 
a close match could produce a lot of distortion.


--
David Woolley
Owner K2 06123

On 05/07/2019 18:55, Jack Brindle wrote:

Lets step back a bit and look at the system here. The K3, with ATU, drives into 
the BPF, when then drives into the external ATU and finally the antenna.
The external ATU takes care of the antenna matching, and should present a 50 
ohm load to the BPF. The BPF, because of its design, should present a 50 ohm 
load to the ATU as well, so everything is matched there.
Before anyone jumps on this, remember the signals go both ways, outbound for 
transmit, inbound for receive. Also, we have a fundamental principal thrown at 
every EE student, that for best transmission of signal, the source and load 
impedances should match.


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Re: [Elecraft] Elecraft KX4

[David Woolley]

In my experience, radio amateurs behave like the general public with 
respect to intellectual property; they generally only respect property 
rights in physical objects.  They'll copy magazine articles without 
paying royalties to publisher, play videos at clubs in spite of the home 
use only warnings, etc.


Much experimentation with equipment is probably legally dodgy, although 
I think there are patent exemptions for experimentation, but possibly 
not for subsequent use beyond validating the design,


In terms of only supporting official versions, there are techniques, 
such as digital signatures, to identify official firmware, even if 
people violate trademarks.  Android is open source, but is still trusted 
for some secure applications.


I suspect ELecraft do actually support modified hardware, which most 
people wouldn't.


Incidentally a lot of the original developers of the internet (before 
commercialisation) were radio amateurs.  One of the big reasons that we 
have TCP/IP now and not something based on X.25, and the OSI model, is 
the open source nature of the key implementations.


--
David Woolley

On 01/07/2019 19:10, Alan wrote:
The software was copyrighted, but that didn't prevent some hams (in 
Germany as I recall) from running a reverse compiler on the code, making 
a few minor changes, and re-compiling it so they could make pirate chips.


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Re: [Elecraft] K4 pre-distortion?

[David Woolley]

I don't think any automatic noise reduction system is intended for use 
on Morse code.  The way to reduce noise on that is to use a narrow filter.


NR is really only intended for speech (or in the wider world, music). 
The key characteristic is that only a small part of the spectrum is 
important at any one time, but that part is continually changing.


NR systems try to work out which parts of the audio spectrum are 
important and which are not, and construct filters to remove the latter. 
 For CW anything other than the immediate area around the signal is 
unimportant, and it is not continually changing.


The only way you could do better with Morse is by recognizing the signal 
and regenerating it as a pure keyed tone.


The human brain and ear are actually rather good at noise reduction; the 
problem is that they tire easily.  NR attempts to make listening less 
tiring, not to change a signal from unreadable to readable.


--
David Woolley


On 16/06/2019 07:39, Dave wrote:

The K3 noise reduction is very poor, I have never found it useful on SSB,
and certainly not on CW.


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Re: [Elecraft] Help with IF Noise, DSP Noise, NR settings

[David Woolley]

The below statement surprised me.  That is not how noise blanking 
normally works; normally it will suppress  any wide band pulse.  The 
typical arrangement uses a high bandwidth, low delay, path, to detect 
the pulse.  It can then mute the signal path by the time the pulse gets 
through the narrower filters on the main path.  That will happen with 
single, or randomly spaced spikes.


--
David Woolley
K2 06123

On 13/06/2019 14:09, Bob McGraw K4TAX wrote:
The Noise Blanker only affects repetitive pulse noise such as ignition 
type noise.  Lightning and atmospheric is random noise.



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Re: [Elecraft] K4: superhet vs. direct sampling

[David Woolley]

On 05/06/2019 13:23, W2xj wrote:

Direct sampling has no image issues.


That's because they are called aliasing issues!

--
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Re: [Elecraft] The K4's new noise reduction

[David Woolley]

There is a good reason why cross-posting email is a bad idea.  This 
failed on elecraft...@groups.io  Could anyone replying please use just 
the standard elecraft list.


On 31/05/2019 21:22, David Woolley wrote:
I would think that, at best, there would be no  benefit over using a 
fixed filter, optimised for the mode, and at worst, they would 
completely break the mode.


The ideal digital mode signal looks like noise!  COFDM as used for ADSL, 
digital TV, digital radio, and 4G mobile phones gets quite close to that 
ideal.





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Re: [Elecraft] The K4's new noise reduction

[David Woolley]

I would think that, at best, there would be no  benefit over using a 
fixed filter, optimised for the mode, and at worst, they would 
completely break the mode.


The ideal digital mode signal looks like noise!  COFDM as used for ADSL, 
digital TV, digital radio, and 4G mobile phones gets quite close to that 
ideal.


--
David Woolley
Owner K2 06123

On 31/05/2019 18:13, John Stengrevics wrote:


The K3S’ NR algorithm is not operable on digital modes.  Will that be the case 
on the K4 as well?


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Re: [Elecraft] Reflector format

[David Woolley]

I believe with Outlook, you can drag the contents of a MIME digest email 
into a folder.


Although there isn't anything native, for this, in Thunderbird, there 
appears to be at least one add-on (undigestify) that will do most of 
this.  A quick skim suggest that it expands to the current folder, so 
you may have to do an extra move.


Except for a bug that doubles Re: in the subject line, you can pull out 
individual messages even with bare bones Thunderbird, and reply to them 
with correct threading.


--
David Woolley

On 21/05/2019 21:28, Don Wilhelm wrote:
If you receive the individual emails using a good email client running 
on your computer, you can do just as you requested.  Unfortunately, it 
does not work that way for the digest nor if you are reading via webmail.





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Re: [Elecraft] Sensitivity - Was K4 Observations

[David Woolley]

These techniques all end up using more bandwidth than a simple scheme, 
and the larger bandwidth itself increase the N in SNR.


There is actually a theory for the case of idealised white noise and no 
other degradation  (both of which are likely to be assumed in the cases 
previously discussed), that sets a theoretical limit to the error free 
digital communication rate of channel, based on bandwidth and SNR.  This 
is the Shannon - Hartley theorem, and states that the capacity in bits 
per second is:


bandwidth * log2 (1 + Signal / Noise)

Note that this formula still has a positive result even if the signal is 
only minutely greater than zero.


The holy grail of communications coding is to get as close as possible 
to this without having excessive latency.


Maybe a better figure of merit for these, "below the noise" digital 
systems would be to quote the channel capacity as a percentage of the 
Shannon limit.  I think the system used for 5G mobile phones get very close.


One does have to be careful with bits per second, as I understand that 
FT8 relies on some parts of transmissions carrying less bits than needed 
to encode the characters in the standard code used, e.g. the number of 
bits actually represented by a call sign is log2 (number of possible 
callsigns) and the number encoded in FT8 is log2 (number of active FT8 
callsigns).


--
David Woolley
Owner K2 06123

On 19/05/2019 19:15, Joe Subich, W4TV wrote:


There is one place that digital modes (like those by Joe Taylor and
associates) can improve the decoded SNR beyond simply reducing the
detection bandwidth.  If the modulation/encoding supports N states
but the encoding only uses M of those states, the decoding software
can make use of the "sparse constellation" to recognize states that
are impacted by noise and select the "closest" valid state.

This "coding gain" can improve the overall SNR beyond that provided
simply by the "matched" (or optimal) noise bandwidth.  However, with
all amateur modes (CW to FT8 & FT4) the majority of the SNR improvement
over SSB (or AM) is simply due to the use of optimal bandwidth to
reduce extraneous noise in the detector bandwidth.  Even with SSB,
properly tailoring the IF bandwidth will make several dB difference
in the detected SNR.  For example, a 2 KHz bandwidth (500 - 2500 Hz)
can provide significant improvement over a 2.8 KHz bandwidth (200 -
3000 Hz) under noisy conditions.



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Re: [Elecraft] K4 Observations

[David Woolley]

Unfortunately, the amateur radio world behaves like popular culture and 
hijacks engineering terms and redefines them.  Nearly every radio 
receiver nowadays is largely an SDR, but the amateur community tends to 
use the term in a more restricted sense.


What I think is meant by Full SDR is what, more correctly, would be 
described as direct sampling.


However, the really key point is that Elecraft's main skills are with 
analogue electronics. To the extent that the K4 has no analogue front 
end, it really doesn't benefit from the company's core expertise 
(although low phase noise clocks may also be one of their skills).


Personally, I suspect that there is significant analogue processing 
before the A/D convertor (the front end) and that is what will give it 
any edge it has over the competition.


A/D convertors are essentially commodity items, to the only real input 
the Elecraft desginers will have is setting the price point.


--
David Woolley
Owner K2 06123

On 19/05/2019 04:09, Buck wrote:
The radio is full SDR as opposed to the analog front end of the K3. 
However an option, the K4HD, is a superhet receive function.  Like 
previous Elecraft radios, this can be added later if you think you need 
it.  Preliminary is that it will not be necessary unless you operate in 
the presence of strong stations (multi-multi).



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Re: [Elecraft] Measuring SWR (Long)

[David Woolley]

A typical transmitter does not reverse terminate the transmission line 
with its characteristic impedance, so most of the reflected power gets 
re-reflected as forward power.  Reflected power isn't necessarily lost 
power.  At least at lower frequencies, it is likely to present a much 
higher impedance.  A final that did accurately terminate the line would 
be rather inefficient.


A more important issue with SWR is high SWRs can cause clipping (you 
need a larger voltage swing if the load is higher (assuming purely 
resistive for the moment), or take it outside the safe operating area of 
the output devices.


Those may cause problems at quite low SWRs, but they actually depend on 
the complex impedance, so on some parts of the Smith chart circle you 
may be completely safe, but on others, you might kill the finals.



On 09/04/2019 22:39, Roger D Johnson wrote:
For an interesting discussion..."What happens to the power that's 
reflected?"


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Re: [Elecraft] Tinnitus and the K3 RX EQ and Related Variables

[David Woolley]

I would expect an audiologist to consider 3kHz as a high frequency, as 
they are generally interested in speech intelligibility, and hearing 
aids are not, generally, high bandwidth devices.


It's also high in musician's terms, being three and a bit octaves above 
middle C.


Someone with age related loss could easily be about 40dB down at that 
frequency.


On 27/03/2019 22:19, Walter Underwood wrote:

If so, ask them whether they consider 3 kHz to be high frequency.


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Re: [Elecraft] Macintosh version of Elecraft KX3 Utility

[David Woolley]

I assume you mean that has been compiled for, as if you can compile it 
you can probably compile if for many different architectures.


However ARM is not a single machine type.  There are many different ARM 
family devices with different instruction sets.  You would probably want 
a specific Raspberry Pi build.


On 27/03/2019 22:13, Andy McMullin wrote:

I wonder if a better answer would be to push for versions of the utilities that 
compile on an ARM chip so that it could be run on a Raspberry Pi.


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Re: [Elecraft] KXPA100 Input Current vs Output Power

[David Woolley]

Whilst I can't give you quantitative answers, I would expect there to be 
a constant term and a square root power term, so my guess is that 50W 
would take about 80% of the 100W current and 10W about 38-40%.


These are peak envelope currents.

--
David Woolley
Owner K2 06123

On 22/03/2019 14:51, Tim N9PUZ wrote:

Is there a chart or formula that describes the input current required for a
KXPA100 amplifier at various power output levels? In a battery operation
scenario I'm curious about the current draw at say 50W output vs. 100W
output.


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Re: [Elecraft] Setting band edges on the K3

[David Woolley]

The UK 5MHz allocation is not a single continuous allocation.  It is 
more like number of spot frequencies with allowances for different 
bandwidths.  Applying frequency fencing would need consideration of 
modes and filters as well as frequency.


In general, I believe that Elecraft set frequency limits based on the 
destination country, although I don't think they can cope with 
essentially spot allocations.


I believe there are ways of changing the allocations in the field, but 
they are not in the public domain and users have to demonstrate 
authorisation for the frequency.


--
David Woolley
Owner K2 06123

On 16/01/2019 09:08, ANDY NEHAN wrote:

I have searched the manual etc. and cant find a way of setting the band edges. 
By which I mean the frequencies outside of which the transmitter will not 
function. Here in Europe (as elsewhere I believe) different countries have 
different band edges - this is particularly so for the 5MHz band. It would be 
all too easy for me to respond to an FT8 CQ (for example) from a European 
station and find that I was transmitting outside of the UK 5MHz band. OK so I 
can fix my transmit frequency but it would be nicer if I could set band limits.
Have I missed something - is this facility hidden somewhere??
Andy G4HUE, K3, KPA500, KAT500, P3 owner.



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Re: [Elecraft] Query for new DSP features

[David Woolley]

The part at 1:03:00 involves a signal that had a large impulsive 
component, and was treated with a combination of noise blanking and 
noise reduction.  Applying pure noise reduction wasn't going to help. 
You can actually see from the pure noise reduction example they played, 
that they were not comfortable with trying to do pure noise reduction on 
a signal that wasn't easily copyable without it.


More importantly, nowhere from the 46 minutes mark do they describe 
their algorithms, although, as open source code, it will be possible to 
find them.


I would assume that the K3 uses LMS.  The spectral one needs similar but 
greater processing to that needed in the phase shifting proposal.  It 
needs greater, in that the it has to compute the parameters by which to 
multiply the FFT bins on the fly, whereas the phase shifting case only 
needs to compute them when you turn the control knob.  Consequently it 
is subject to the same performance question:  does the K3 hardware 
actually have enough processing power to run the algorithm.  (I assume 
LMS is used because the processing power requirements are rather less.)


I don't know whether it has the power needed.

My description of the general problem of noise reduction actually more 
accurately fits the spectral processing model. I believe LMS is trying 
to achieve a similar effect, but in a more computationally efficient manner.


Pure morse code doesn't actually need complex noise reduction, as simply 
using a narrow filter will do the same thing as a good spectral noise 
reduction algorithm would attempt to achieve.  It can, though, benefit 
from noise blanking.  I say morse code, because a literally CW signal 
can get perfect (Gaussian) noise reduction by using an infinitesimally 
narrow filter.  Actually, for a fair test, they should have also shown 
the result of applying a very narrow filter to the power-line noise example.


Nothing in the part of the talk I listened to addressed the problem of 
distortion caused by the suppression algorithm, in particular the 
non-linearities caused by modifying the parameters on the fly.



On 15/01/2019 02:53, Wes Stewart wrote:
https://www.youtube.com/watch?v=FrVDL_-HOds starting at 41 minutes. 
Particularly at 1 hour 3 minutes.


On 1/12/2019 9:51 AM, David Woolley wrote:

Do you have a reference for an algorithm that will do this?




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Re: [Elecraft] New DSP Idea

[David Woolley]

Assuming that there is enough processing power available, and the 
architecture physically allows the mixing, manually steering either the 
peak or the null should be achievable.  There is a slight subtlety in 
that one is trying to achieve a constant time delay at RF, not a 
constant phase change, but, if RF is sufficiently higher than the the 
baseband, it will be a good approximation, and the hardware devices 
being quoted probably have the same defect.


Automatically getting a direction is only accurately achievable if the 
interfering noise is isotropic, at least in the plane containing the 
line between the antennas. As such, it will not be able to automatically 
get a direction for an interfering signal, unless it can separate that 
signal from everything else, and if it can do that, there may be more 
direct ways of removing the signal.


The only way I can see of performing the computation is in the frequency 
domain.  Although everything starts as just a time delay, the down 
conversion preserves phase not time, so I think one needs to do a 
Fourier transform, rotate each value by a fixed amount (or one 
accounting for the offset from the carrier not being negligible) and 
then invert the transform.  (There may be better algorithms.)


Because of the discrete nature of FFTs, you would probably want to run 
several overlapping transforms and average their results.


I suspect the current DSP tries to avoid doing a full Fourier transform, 
and even panoramic adapter FFTs don't need to run overlapping transforms.


I think the big question is does the machine have enough processing 
power to do this.

--
David Woolley
Owner K2 06123

On 13/01/2019 01:06, David Gilbert wrote:


these things:

1.  Actually amplify a desired signal (probably 2 to 3 db) at the 
expense of other signals or generalized noise from other directions. 
Hams who put up phased verticals don't do it strictly for the transmit 
gain.


2.  Totally null out an offending signal or noise from a particular 
direction.  Your brain most certainly can't do this.


3.  Give you angle measurements in degrees.

As I said, I consider the add/subtract ability (#1 and #2) to be more 
useful than the simple display of the phase difference (#3), but we 
could have both.


Check this out  https://tinyurl.com/ydfvcauz

It's a hardware implementation of pretty much the same as I'm proposing 
Elecraft do in software, and the hardware version goes for $750.


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Re: [Elecraft] Query for new DSP features

[David Woolley]

Do you have a reference for an algorithm that will do this?

Noise reduction is difficult because any effective noise reduction has 
to recognize what is signal, and ideally what is the part of the signal 
that matters to the human.  The hearing aid industry has been trying to 
do this for years, with limited success.


I think the sort of noise reduction we are talking about here 
essentially tries to decide which frequencies matter and which don't and 
eliminate the latter.  However, it has to do this when what it is trying 
to identify as signal is hidden by noise.


In practice, I think what these systems achieve is increased user 
comfort, rather than recovering signal from noise, as humans are 
probably still a lot better at extracting signal from noise than 
algorithms, but they get tired in doing so.


One consequence of selective filtering will be a reduction in total 
audio power.  I'd expect the total loudness to go down.  I guess you 
could then renormalise, and increase the signal power to bring the total 
power up to the same level.  However, most of are old enough to have a 
lot of high frequency hearing loss, so one may find that correction 
needed depends on specific hearing loss of the user and the original 
spectrum of the noise; one needs to renormalise the power as waited by 
the hearing sensitivity curve of the user.  I imagine you would need, at 
least, a parameter to determine the degree of renormalisation.


Also, the more aggressive you make this sort of noise suppression, the 
more likely it is to have false positives, and suppress important 
frequencies.  Also, the more aggressive you make it, the more you will 
get distortion as the result of modifying filter parameters on the fly.


Ultimately, though, the sort of noise that these systems are trying to 
remove is random in nature, so you can never be completely sure what is 
signal and what is noise.


(Hearing aids have a particularly difficult problem in that they are 
dealing with cocktail party noise, where the noise is the summation of 
lots of things that would, individually, be signals.)


(The ultimate noise reduction system would be one that recognized the 
speech and regenerated it, complete with characteristics of the original 
speaker.  However, doing that really well can only be done by looking 
ahead several seconds, to be able to interpret meaning from what 
follows, as well as what precedes.)


As a caution, I believe the K3 has two different noise handling 
strategies:  the one I am talking about here, and one designed to deal 
with impulse noise, where you simply cut out a short section of signal 
around the noise pulse.


--
David Woolley
Owner K2 01623

On 12/01/2019 04:38, Mike Lichtman wrote:

I would like to see an improved Noise Reduction that doesn’t lower the volume 
or distort as much.



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Re: [Elecraft] KAT 500 and open wire

[David Woolley]

Don:

1) made a distinction between feedpoint and load impedance, which led me 
to believe the load was the antenna, and the feedpoint the transmitter end;


2) said that the feedpoint impedance depended on the length of the line 
and the frequency, which further supported that interpretation.


However, considering your definition of feedpoint, and consider balanced 
twin feeder.  Even with a perfect choke at the feedpoint, there will be 
unbalance at the transmitter end, when using designs, like the K series, 
that feed against chassis.  In particular, consider a feeder length of a 
quarter wavelength.  As well as the intended differential mode signal, 
you will also excite the feeder as a quarter wave vertical against the 
chassis and, presumably, ground, if you don't choke at the transmitter end.


My gut feeling is that having a good match to the feeder is an 
oversimplification, but I need to think about that a bit more.


Incidentally, is the 4:1 "current mode" balun configuration really 
purely current mode?  It seems to me that it is behaving as a 
transformer as well as as a choke.



On 07/01/2019 02:12, Jim Brown wrote:
I think we're confused here about the meaning the words "feedpoint 
impedance." It is the impedance of THE ANTENNA at the point where the 
feedline is attached, and it is determined entirely by the antenna, 
INCLUDING the common mode circuit of the



I don't know of a way to EFFECTIVELY choke a feedline that is not matched to 
the antenna.
a very good choke must be AT THE FEEDPOINT


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Re: [Elecraft] KAT 500 and open wire

[David Woolley]

The feedpoint impedance DOES depend on the characteristic impedance!

Taking pure resistive cases (real characteristic impedances aren't), and 
lossless lines, a 75 ohm load at the end of a 75 ohm transmission line 
will have a feed point impedance that is a constant 75 ohms, whereas a 
75 ohm load on 300 ohm feeder will have a feed point impedance that 
swings from 75 to 1200 ohms.


--
David Woolley
Owner K2 06123

On 06/01/2019 21:40, Don Wilhelm wrote:
The feedpoint impedance to the transmission line can vary from quite low 
to quite high dependent on the frequency, the length of line, and the 
load at the far end.  It does NOT depend on the characteristic impedance 
of the transmission line.




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Re: [Elecraft] How to unsubscribe from reflector?

[David Woolley]

On 30/12/2018 00:04, W2xj wrote:

Work for most large media companies worth billions and writing down passwords 
will have security escorting you out of the building, a lost pension and a 
major followup security investigation.


Passwords have become unworkable as a security measure.

Too many sites need them, and some of those will get compromised,leaking 
your password;


Using a different one for each site means it is difficult to remember 
them all;


Rules that you must not write them down result in the same password 
being used across both well secured and poorly secured servers.


Rules that passwords be changed frequently, combined with the need to 
have many different passwords, results in weak passwords, as inventing 
good ones, that are different form other people's, is difficult.


Any organisation where security is important should not be relying 
solely on passwords.


On the original subject, most technical mailing lists obey the 
convention that mail to -owner@ will go to a human 
administrator (I would say that any well managed list should do this). 
Failing that, many will forward anything not understood to a human (or 
reply with help saying how to contact a human) if mail is sent to 
-request@ and doesn't contain a valid list command.


Most such lists also have a number of guidance links in the message 
headers, e.g., for this list:


List-Unsubscribe: ,

List-Archive: 
List-Post: 
List-Help: 
List-Subscribe: ,


Amongst other things, the help reply says you can send this to the 
-request address:


unsubscribe [password] [address=]
Unsubscribe from the mailing list.  If given, your password 
must match
your current password.  If omitted, a confirmation email will 
be sent

to the unsubscribing address. If you wish to unsubscribe an address
other than the address you sent this request from, you may specify
`address=' (no brackets around the email address, and no
quotes!)


This does rely on the subscribing address being still valid, but if it 
is not, the mail bounces should eventually get the subscription 
terminated, automatically.

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Re: [Elecraft] K2 with KPA-100

[David Woolley]

Unfortunately the KAT100-2 doesn't seem to be available any longer, even 
though it is still described on the man page for the tuner.

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Re: [Elecraft] Noise-cancelling headphones mystery

[David Woolley]

Noise cancelling headphones rely on the distance between microphone and 
ear being a small fraction of the audio wavelength.  At high 
frequencies, that will be impossible to achieve, and, even if you put in 
a compensating delay, the path to the  ear is going to depend on the 
direction of the source.


--
David Woolley
Owner K2 06123.

On 09/12/2018 16:40, CUTTER DAVID wrote:

ncies.  If your hearing takes you higher, the noise-cancelling has finished by 
then.  This is probably not the ability of the sensing mic but the circuitry 
and/or room acoustics, echo, etc.  I'm a little out of date on the subject but 
that's probably the essence of it


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Re: [Elecraft] FS: New CM500 headset

[David Woolley]

The National Health Service in the UK tends to use slightly modified 
commercial designs that are maybe a couple of years old, and their input 
costs are something like that.


However, I don't think self fitting would be allowed in the UK, as 
setting the gain too high can cause unnecessary damage to residual 
hearing, and many new users would set it too low to be effective. 
Mobile phones are also not accurately calibrated.  The other reason for 
not allowing self fitting of real hearing aids is that hearing loss can 
be a warning of more serious things, like brain tumours, and a proper 
audiologist will refer patients for more detailed investigation if there 
are hints of that.


Also, this is only going to work with open fit aids.  You can have just 
a few sizes of fitting.  They do tend to work well for people with age 
related loss, where most of the loss is in the high frequencies.  People 
with more complex losses require custom made ear moulds, and the most 
difficult cases actually require aids that change the frequency of the 
sounds.


It looks like Olive only address the easy end of the market.  I'm not 
even sure it would be classified as a hearing aid in the UK (hearing 
aids are prescription only - RX Only in US terms).  I can find none of 
the technical documentation that I would expect for a normal aid, and, 
in particular, I can find no graphs showing the performance envelope. 
It looks like it has something more like an in the ear headphone fitting 
than the sort of fitting you would expect on a normal hearing aid.


It has enough output to damage hearing if used incorrectly.

It looks to only have one microphone, and loss of directionality is one 
of the big problems with using hearing aids.  Multiple microphones allow 
some beam forming.


Hearing aid pricing is complex, because the marginal cost of manufacture 
is quite low, but there are are high R costs for the noise reduction 
and automatic adaptation.  A lot of the R will be recovered by private 
buyers paying a large premium for the latest technology (a bit like 
films take a lot from theatre audiences, but eventually are sold cheaply 
to TV stations).  Also the service costs in prescribing and maintaining 
can be high.  For the NHS these dominate the cost of the physical 
instruments.


--
David Woolley


On 28/11/2018 02:48, John Simmons wrote:
A friend of mine told me about the new Olive hearing aids coming from S. 
Korea. They are currently being sold only on Indiegogo and one ear is 
$139 instead of the multikilobuck jobs. I'm interested to hear how they 
work for him. You configure the amplification and response curves using 
a smartphone app.



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Re: [Elecraft] FS: New CM500 headset

[David Woolley]

Are you sure of those figures?  30dB is normally only considered mild 
loss.  15dB is in the normal range.


I have at least 40dB. across the spectrum, in one ear, and 15dB at 
500Hz, degrading to 70dB at 8kHz, in the other, and I'm only classed as 
having a moderate loss.  These figures are a few years old, so the 
current ones are marginally worse.


If you have severe enough loss to need full ear moulds, I think all 
modern aids have various options to directly feed the aid with, at least 
mono, audio, and some headsets will naturally work with aids that can be 
set to an induction loop setting.


Typical options for full stereo, are blank headsets, that just create an 
induction field, ear hooks that hook over the ear and create an 
induction field, and direct audio input shoes that plug into over the 
ear aids, and allow a copper connection to the aid.


For most aids you can get a bluetooth adapter, that you wear on a, 
conductive, neck loop.  This is generally mono.  You can typically 
provide a copper audio feed to these, in which case there is no 
bluetooth (the near field link uses a different protocol, and at HF, not 
SHF), or you can remote bluetooth adapters, which have low latency, as 
well as the normal bluetooth adapters, with their high latency.


The Phonak brand name for this feature is ComPilot.  My aids are Oticon, 
for which it is ConnectLine.


I think the open fit aids, used by people with, typical, age related, 
high frequency loss may be more of a challenge, as they are designed to 
pass the low frequencies directly and only amplify the high ones.


--
David Woolley
Owner K2 06123

On 27/11/2018 01:20, Edward R Cole wrote:

> Firstly, I have extreme hearing loss.  Without my Phonac-Silvia hearing
> aids the world it very quiet.  I have something like 30-dB loss in both
> ears so not wearing

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Re: [Elecraft] [K2] External Fan Hum

[David Woolley]

Most "DC" fans used for equipment cooling use what are fundamentally 
synchronous AC motors, but with the twist that the the AC frequency is 
adjusted to match the rotation rate.  (You can also consider them as 
stepper motors, operating at maximum slew rate.)


That's what "brushless DC motor really means".

I'd expect to see an AC field, although at a multiple of the rotation 
rate, and with quite small gaps between stator poles, so with the 1/3 
power near field fall off, quite weak at distances.  On the other hand, 
they will be square wave, before the inductances gets to them.


--
David Woolley
Owner K2 06123


On 07/11/18 14:56, Don Wilhelm wrote:
The DC fan may have a magnetic field, but it would be constant instead 
of alternating polarity 120 times a second.


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Re: [Elecraft] CODEC

[David Woolley]

But if they want to install a third party time sync program they are 
better off installing W3HCF's definitive implementation of the NTP 
protocol, rather than a program that was, I believe, really designed for 
Windows 3.1/95.


In 06/10/18 21:15, Larry (K8UT) wrote:
The user has two choices: use Regedit and mess with the Windows registry 
to reduce the interval; or install a time sync program. For most, the 
second option is easier.




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Re: [Elecraft] CODEC

[David Woolley]

There should be very little reason to use Dimension 4, with step updates 
at fixed intervals.  The full implementation of ntpd is available for 
all the Windows NT family, i.e. everything after Windows 95, and 
versions or w32time that can be configured to implement the older 
version of NTP  have been supplied with Windows since at least Windows XP.


The standard ntpd always works by managing clock frequency, so there are 
no abrupt time steps unless something has gone sufficiently wrong to 
result in a step of at least 200ms.  w32time can be configured to work 
that way, although generally installing the standard (reference) version 
of ntpd is preferred.  (ntpd can be configured to almost never step the 
time.)


Although Windows is not a good platform for time keeping, both these 
approaches ought to produce times accurate to about 20ms, and only 
slowly changing with time.  In some circumstances, Linux can produce 
several orders of magnitude better results.



On 04/10/18 22:32, Mike Greenway wrote:

As previously posted the problem had nothing to do with CODEC or the K3S.  
Problem turned out to be the time update of the computer by Dimension 4.  I had 
it set for updates every 1 sec as I didn’t think that was a problem.  I now 
have it set for 30 Mins and probably and hour would not hurt anything as every 
15 secs it does about .049 correction on my computer.  I don’t think it is 
abnormal for the Rates on WSJT-10 to jump out of range when a time update is 
done to the computer.  Something you cant see on WSJT-X or JTDX.  Thanks to all 
that wrote with suggestions, all of them good.  73 Mike K4PI




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Re: [Elecraft] Mail List Procedure Question

[David Woolley]

I'm replying to this from the digest!

There are two ways of taking the digest.  With good mail programs, the 
best way is the MIME digest format.  Although the details may vary, good 
mail programs will allow you to decompose the digest.  In the case of 
Thunderbird/Iceweasel, it displays the concatenated messages, with 
specially formatted header lines, and provides access to the individual 
messages as though they were attachments.


There is a minor bug in that, when replying to a reply, Thunderbird adds 
an extra "Re:", but that is easily fixed.


Doing it this way, rather than just editing out the rest of the digest, 
has the added advantage that a correct In-Reply-To header is sent, that 
can help threading readers.


(What  I really hate is where people ignore the warning at the top of 
the digest, and simply copy the whole digest, or that part after the 
message to which they are responding.  That cuts short the next digest 
and also forces one to plough through lots of old postings, possibly to 
find that the culprit has overflowed the digest size limit and there are 
no more real items in the digest.)


--
David Woolley
Owner K2 06123

On 30/06/18 15:09, Lee Murrah wrote:

I am receiving messages in the digest mode. I see that most replies to topics 
include the text of the prior message and a modified subject line in the form 
you would expect when replying to an email.  However, there is no way to reply 
directly to a topic and include the prior text and subject line as far as I 
know.  How can I do this?



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Re: [Elecraft] KPA-1500 ATU not working well

[David Woolley]

I'm not clear whether you are talking about the SWR before or after the 
tuner, but efficiency is determined by the load seen by the PA, which 
has two degrees of freedom (reactance and resistance), both of which can 
vary either side of the ideal.  SWR reduces this to a single variable, 
that doesn't even respect the sign of the deviation from the ideal load. 
That means that efficiency may even be better than the nominal 
efficiency at a particular SWR, whereas that same SWR can also produce a 
lowered efficiency.  (Similarly, an SWR may destroy a PA or be safe, 
depending on the fine details.)


In particular, a higher load resistance may result in a higher 
efficiency, at the expense of a lower maximum output.  There is actually 
a K2 build option, that winds the output transformer to impose a higher 
load resistance, in order give better efficiencies at low powers.


Tuning across the band will change at least the reactance component of 
the load on the PA.


Also, if input SWR isn't 1:1, I think you will find that the measured 
forward power doesn't reflect what is actually available to go out 
through the antenna.  Whilst some of it will circulate back and forth 
and eventually make its way out in the right direction, some will also 
get absorbed by the PA.


On 22/06/18 20:36, Paul Baldock wrote:
I have found that if the KPA1500 is feeding  a largish SWR (like 1.5:1 
as you suggest) then the drive power required to maintain a constant 
output will vary significantly as you tune across a band. This means you 
have to keep adjusting the power control within a single band. This 
appears not to occur if the SWR is 1.1:1 or better.


I don't know, but I would guess a solid state untuned amplifier 
efficiency is better into a 1:1 SWR  than a 1:5:1. This could lead to 
the dreaded more fan noise.



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Re: [Elecraft] K2 Build: Options Advice

[David Woolley]

The disadvantage is that you will need to unsolder some components.  In 
most cases, I think you can destroy the through holes, but there is at 
least one case where you have to insert a new value in the old hole.


There used to be a, third party, product, called UnPCBs, which provide a 
minimal dummy version of most of the modules, but the sales of the K2 
dropped to a level where it wasn't worth another production run for the 
PCBs for this.


--
David Woolley
Owner K2 06123


On 24/05/18 19:44, AE0MM wrote:

I'm planning to build a K2/10 with the following options:
KNB2
KAT2
KAF2

Is there any disadvantage to building the base K2, then adding the options 
later?

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Re: [Elecraft] KPA500/K3 AUX bus specification

[David Woolley]

You would need to sign a non-disclosure agreement for anything beyond 
the logic level (TTL) and pinout information.  I've never heard of one 
being given out for this purpose.


--
David Woolley
Owner K2 06123

On 29/04/18 21:59, ANDY DURBIN wrote:

Can someone please point me to a definition or specification for the KPA500 - 
K3 AUX Bus.   I have the KPA500 Programmer's Reference but this appears to only 
cover the KPA500 - PC interface.


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Re: [Elecraft] current flow on copper strips

[David Woolley]

I think that thinking in terms of skin depth, is causing a lot of the 
confusion here.  Skin depth is a consequence of how the fields 
representing the electromagnetic pulse propagate in the electron plasma 
of the metal, so is a secondary effect, not a primary one.


This whole thing is better addressed assuming a perfect conductor, so no 
wave penetration, and therefore no skin depth at all.


Far from the tube, the magnetic field is circular.  Immediately outside, 
it parallel to the surface.  Transiting between the two, that means 
field is compressed at the ends of the major axis.  The field density is 
proportional to the current, so the current will be concentrated near 
the major axes end points.


--
David Woolley
Owner K2 06123

On 27/04/18 23:47, Alan B wrote:

My thinking is the current density is uniform in the outer surface of a round 
tube falling according to skin depth at that frequency. At higher frequencies 
there is no current on the inner surface so whether they touch when squashed is 
immaterial, no current there anyway.
What is relevant is the shape of the magnetic field as the tube is 
progressively squashed. As it gets flatter the current distribution moves 
closer and closer to that of a strip. There are no sudden effects.


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Re: [Elecraft] The new KX19

[David Woolley]

Whilst I do understand that this was only a half day special offer, 
could you confirm that the anti-gravity mods reduced the inertial mass 
as well as either the local value of the gravitational constant or the 
gravitational mass?  My previous experience of such technology is that 
the device tries to disappear on a near parabolic orbit, except for 
being slightly limited by air resistance.


--
David Woolley
Owner K2 06123 (low mass and power by design)

On 01/04/18 18:56, kevinr wrote:
Antigravity mods let you 
take the KX19 on camping trips, ocean cruises, or even pedestrian 
mobile. The additional 5 Petawatt power source for the antigravity 
modules necessitates the liquid helium cooling module. Call Elecraft 
today for a quote.

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Re: [Elecraft] KX3 Utility Segmentation Fault in Linux

[David Woolley]

That is much more serious than a warning.  I'd expect it to be 
immediately followed by a crash with signal 3 (abort), rather than 
signal 11 (segmentation fault).  However, if this isn't the standard 
assert routine, I would expect any attempt to actually use hash_table to 
produce a segmentation fault.



The standard assert routine is a macro which tests the condition and, if 
it fails, logs the fact then call abort, which never returns.



On 11/03/18 21:49, Thomas Kluge wrote:

(k3util:2054): GLib-CRITICAL **: g_hash_table_insert_internal:
assertion 'hash_table != NULL' failed
I think this is just a warning but it was followed by a segfault...


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Re: [Elecraft] KPA1500 and FT8

[David Woolley]

I believe at least some of the DSP filters in the K3 are FIR (Finite 
Impulse Response) ones, which should be phase linear.  The roofing 
filters will not be phase linear, so I would think you could get away 
with using a narrow DSP filter, as long as you used a relatively wide 
roofing filter.


This will still leave the ADC, and the analogue circuitry between the 
roofing filter and it, open to overloads, but will protect the sound card.


On 04/03/18 21:15, Jim Brown wrote:
There is a VERY good reason why WSJT developer, K1JT, advises users to 
use wide IF bandwidth, and it's NOT the panoramic display. The reason is 
that filters introduce phase shift in the passband, and phase shift is 
the enemy of good decoding. The same physics, by


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Re: [Elecraft] PA Transistors Maintenance in K2

[David Woolley]

As far as I can tell, no torque settings are given for any of the 
fasteners, wouldn't it be an idea to provide those, for people who do 
have suitable tools.  Generally there are just warnings not to over-tighten.


On 28/10/17 20:24, Mel Farrer wrote:

  If the people at Elecraft have done their job and mounted the transistor 
properly with the correct torque on the mounting hardware procedure, no 
additional maintainance is required.


--
David Woolley
K2 06123

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Re: [Elecraft] KX3 with BL2 Question

[David Woolley]

On 05/10/17 14:19, John Oppenheimer wrote:


The Balun, both 1:1 and 4:1 is modeled with a perfect conventional
transformer block "A." The KX3 ATU is modeled with the L-C network block
"LC1." A five foot RG-58A/U between the Balun and KX3 is added.


A perfect transformer is not a good model for two reasons:

1) The number of turns is too low to have a leakage inductance that is 
large enough to ignore, especially at lower frequencies; I think this is 
particularly true for the 4:1 configuration;


2) The general wisdom seems to be that you want a lossy core, so that 
the common mode current sees more of a real than imaginary impedance.


--
David Woolley
K2 06123
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Re: [Elecraft] Items you think you can depend on

[David Woolley]

But the electrons only get less than a micron back before they get sent 
forward again, and they've only had about 1/120th of a second to rest. 
You are lucky they are not unionised, with those working conditions!


--
David Woolley
K2 06123


On 04/09/17 19:09, Ken K6MR wrote:

Yes, but those electrons are really tired after all the work they did and need 
to go home to rest and regenerate….

Ken K6MR

From: Fred Jensen<mailto:k6...@foothill.net>



Yes indeed!  For many years, unscrupulous electric power companies have
been capitalizing on the fact that they send electrons to our house and
charge us for them, we toast the bread with them, and then ... get this
... the electrons we paid for go back to the power company!!  They get
away with this because none of us ever inspect our electricity closely.



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Re: [Elecraft] Items you think you can depend on

[David Woolley]

This appears to be cross-posted between mailing lists, something I would 
not recommend.  I'm dropping the one to which I am not subscribed.


There are two classes of "12V" equipment:

* equipment designed for lead acid batteries, of which amateur radio 
equipment is typical;


* computer equipment.

The former is actually designed for 13.8V with a wide tolerance, 
although mainly downwards.


The latter is designed for 12.0V with a tolerance of maybe 5%, and 
expectations of rather better.  Depending on what it contains, it may 
actually tolerate a rather wider range.


--
David Woolley
K2 06123

On 05/09/17 01:09, Phil Kane wrote:

That is true for Elecraft equipment but I was referring to "generic" 12V
stuff.  For example, some "12 V" things that I use are external disk
drives, powered USB hubs, radio accessories, and computer peripherals of
all sorts.  Some manuals list this, sometimes we are lucky just to get
an instruction sheet with pictures let alone text.


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Re: [Elecraft] K3S Noise reduction Test

[David Woolley]

Noise reduction is about reducing subjective noise for the listener, not 
about reducing some engineering measurement.  An instrument is likely to 
generate some very simple, or even pure tone, signal.  With the sorts of 
strategy used for noise reduction, and very aggressive settings, you 
could obtain almost perfect results on such a signal, but those same 
settings would make human speech completely unintelligible.


The big challenge for noise reducers is deciding what is human speech 
and what is noise. That's much more difficult than identifying a pure tone.


The other sort of test signal that might be used, and the one that is 
implied by the definition of noise factor, would be white noise, and 
noise reducers will have no effect on the signal to noise ratio there. 
They will reduce both equally.


The human brain is actually rather good at noise reduction of human 
speech, but it gets tired.  The aim of noise reducers is to not do quite 
as well, but remove the fatigue element from the human.


As I've noted before, where the real money is in noise reduction 
research is in the hearing aid industry, where the noise can be 
particularly challenging, as it is generally mixed up human speech form 
the other people in the restaurant.


--
David Woolley K2 06123

On 20/06/17 20:44, GRANT YOUNGMAN wrote:

You might want to look at actual (S+N)/N data.  I’m not sure the visual “test”  
tells the full story, since these are complex waveforms.

I did extensive measurement several years ago on the NR functions of the v1 and 
v2 firmware versions of the TenTec Orion (for some reason, noise reduction not 
being “magic” surfaces everywhere as a contentious issue), and the measured 
data did not always match what things ”looked like”.   Not saying they don’t 
here, but it’s improvement in (S+N)/N that’s the end objective of NR regardless 
of what the screen shot looks like.

SpectrumLab can measure this directly.  http://www.qsl.net/dl4yhf/spectra1.html


On Jun 20, 2017, at 3:13 PM, wa9fvp <rep...@willcoele.com> wrote:

If you look at my data, there’s very little noise level difference in the delay 
settings.



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Re: [Elecraft] [K3S] JT65-HF Beginner

[David Woolley]

Using a GPLed compiler and most of the GPL tools doesn't result in a 
requirement to licence under the GPL.  In particularly, gcc is often 
used to compile proprietary code.


Using GPL libraries does, except where those libraries implement 
functions that would normally be included with an operating system (e.g. 
the standard C library).


Some tools put a significant amount of template code into the output, 
but those are normally licensed under LGPL, rather than GPL.


--
David Woolley K2 06123

On 28/05/17 16:32, Kevin Stover, AC0H wrote:

If the program was written with GPL tools, compilers, libraries, dll's,
etc..., as WSJT-X was, he is required to release the code.


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Re: [Elecraft] [KPA1500] Input Power

[David Woolley]

I'm suggesting that using a pad to control gain is bad design.  A pad is 
going to necessary to provide the correct 50 ohm termination for the driver.


I would suggest that the main gain control component on the KPA500 was 
T2, although a more detailed analysis may show that some or all of the 
passive components between its secondary and the FET gates are involved, 
as well.


In any case, I don't think Elecraft are going to comment on how the 
achieve FCC compliance, on the 1500, in too much detail, in case it 
could be interpreted as instructions for subverting that mechanism.  At 
least not until they have approval.  I notice total silence from the 
insiders on this, and the previous similar thread.


--
David Woolley K2 06123

On 13/05/17 15:59, Dr. William J. Schmidt, II wrote:

So are you saying that the KPA500 is a bad design?

I'm not aware of a single non-CB amplifier that doesn't use an input pad...



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Re: [Elecraft] [KPA1500] Input Power

[David Woolley]

Using a pad would be bad design, as simply increasing the level of 
negative feedback would help reduce distortion.  The only way one could 
achieve a repeatable gain close to 15dB would be with negative feedback.


Moreover, I assume it is an FCC condition that modification by the end 
not be easy.  You can assume that CB users wanting to use illegal powers 
have access to soldering irons.


Also, I would assume that the design gain is actually less than 15dB, to 
allow for component tolerances.


--
David Woolley K2 06123

On 12/05/17 02:43, Dr. William J. Schmidt wrote:

All of those popular devices have gain more than 15 dB... so there is a pad in the amp to 
keep the gain at 15 dB. One would think that a "tweak" will evolve to modify 
the pad (and possibly the firmware) to eliminate this bothersome limit.


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Re: [Elecraft] Another really good reason to come to the Visailia DX convention this weekend...

[David Woolley]

I don't believe that it is legal to market a power supply that only 
draws current on input peaks in either the USA or EU these days.  Power 
supplies are supposed to spread the current demand over a significant 
part of the cycle.  I believe this is done by having a relatively low 
value capacitor on the mains side and relying on the switching regulator 
to compensate for the wide voltage variations across each cycle.  I 
believe that even applies to wall warts.


This "power factor correction" will not be perfect, so the peak current 
will still be more than for a resistive load.


--
David Woolley K2 06123

On 25/04/17 04:51, Jim Brown wrote:

The reason for using 240VAC is to reduce the IR drop in the AC line,
which, BTW, is not sinusoidal, but rather pulses that charge the filter
caps at the peaks of each cycle. So the drop in the wire is even greater
than Ohm's law appliced to a sine wave would predict.


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Re: [Elecraft] KPA1500 amplifier with built-in ATU, separate power supply

[David Woolley]

Real PA designs are very far from correctly reverse terminating the 
transmission line.  The maximum power transfer theorem is a complete red 
herring in this sort of situation.  For example, on the top of page 12 
of the third edition of the Art of Electronics, immediately after 
setting the maximum transfer theorem as an exercise, they point out that 
ordinary output stages are operated far from that condition.


The only case in which you might get reverse termination, is if there 
was a (typically ferrite) isolator.  In that case, the PA wouldn't care 
about the mismatch (at least not for an ideal isolator), but the 
terminating resistor in the isolator might glow red or white if you 
shorted or opened the output.  In practice they are normally microwave 
devices, but I suppose they may be used in professional HF systems.


In real systems, most of the reflected power bounces straight back out 
again when it hits the PA, to get another chance to be lost in the 
feeder, or even radiated.  Of course this may cause the PA to run out of 
volts, or gain, and clip or distort, or exceed the safe operating area, 
and melt bond wires, or destroy the chip itself.


--
David Woolley Owner K2 06123

On 22/04/17 05:47, John Perlick wrote:


Well, it might incrementally improve the loss in the coax because the reflected 
wave from a high SWR antenna would not be the-reflected at the amp.  It would 
be fully absorbed into the amp which is well matched.



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Re: [Elecraft] KPA-1500: Gain Mod when FCC Lifts 15db Rule

[David Woolley]

As I understand the way things work, they will not get approval for the 
device, if it is easily modifiable to defeat the current limit, so I 
would expect them to play down any modifiability even if it can't be 
classed as easy.


--
David Woolley K2 06123

On 21/04/17 11:43, Richard Thorne wrote:

So if and when the FCC lifts the 15db gain rule, will there be a mod
available to increase the gain capability so a KX3 or KX2 could drive
this bad boy?



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Re: [Elecraft] A little theory.

[David Woolley]

I believe people are confusing Feynman and Sagan.  I think it was Carl 
Sagan who demonstrated the sloppy practices with combination locks and 
did the Challenger enquiry.


I did read some of Feynman's lectures, in high school.

--
David Woolley K2 06123

 tOn 17/04/17 02:32, k...@juno.com wrote:

A long time admirer. For me, his "O ring and a glass of ice water" 
demonstrationwhich kicked the air out of the NASA gas bags during theChallenger Disaster 
inquiry was most memorable. A remarkable man. 72, Tim Colbert  K3HX


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Re: [Elecraft] Amber display for the K2?

[David Woolley]

I'd never really thought about the colour, but I think it is basically 
the natural colour of the combination of liquid crystal and polariser. 
It's not the narrowband green that you would get with a green LED.


Especially if you add in the fact that white "LED"s are really narrow 
band blue LEDs with broadband yellow phosphors, so are not peaking in 
the green, natural variations in colour vision, or colour vision 
defects, could easily cause the colour to be treated as a yellowish 
amber, rather than a reddish green.


I would have thought using green LEDs would have been a more efficient 
use of precious milliamps.


The display is just a seven segment array and has a manufacturer's part 
number, although it is possible it is end of line.  I don't think it is 
custom, or at least not at the time of the original design.


The real problems with making the change are that the LED's are 
integrated into the diffuser and the diffuser is behind the, unsocketed, 
display.  I doubt you could change the colour, except before the first 
build, without destroying the LCD panel.  It is also possible that the 
diffuser assembly is difficult to source; there is no manufacturer's 
part number for that.


--
David Woolley K2 06123

On 05/04/17 22:15, Don Wilhelm wrote:

Tom,

The LCD display on the K2 has "been what it was" from the beginning
(even for Field Test units).
The backlighting is white (LEDs, not incandescent), but the color of the
actual display is green when backlighted.  Actually, it is green when
frontlighted (without the backlight) as well, but more gray than green.

There is no amber LCD for the K2, never has been.  I think some posters
confused K2 with the KX2 (which does have an amber LCD - same LCD as the
K3/K3S and the KX3).

The LCD display is a custom display, so duplicating that custom display
for someone who wants an amber display would be quite an expensive
proposition.  In other words, an amber LCD for the K2 is not practical.




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Re: [Elecraft] What caused long reposts

[David Woolley]

If you are using Thunderbird, I believe the best way is to request the 
digest in MIME Digest mode.  As well as allowing you to page through the 
digest, it also allows you to treat the individual messages as 
attachments, so you can open up the specific  message and reply to it. 
That way, you get the correct subject, and, more subtly, you get the 
correct In-Reply-To header, so that forums and good mail clients can 
properly place the reply in the thread.


That's how I do all replies to this list.

(Note Thunderbird does have some bugs, e.g. I had to delete a redundant 
"Re:" from the subject.  It can also be a little fiddly working out 
which instance of the subject is the correct one in the attachments.)


Unfortunately, the top posting policy of the list reduces the incentive 
to trim posts, meaning people who do end up quoting the digest don't 
think about pruning it.  Failing to prune is also bad for readers of the 
digest, as they have to page over the complete back thread.


This has been top-posted, but also pruned, as it would be for an 
interleaved posting (popularly called bottom posting, although not 
everything need be at the bottom).


On 02/04/17 03:35, Don Wilhelm wrote:



I understand that those steps are more difficult on a smartphone.  It is
easy when using an email client like Thunderbird.  As I have stated, I
suggest receiving individual emails and sorting them into an Elecraft
folder.  That way you can reply to individual posts without the bother
of deleting a lot of information.  I do not receive email on a
smartphone, so I don't have any suggestions for handling that.



--
David Woolley K2 06123.

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Re: [Elecraft] Future KX3/KX2 accessories?

[David Woolley]

Computerised language translation is predicated on good continuous 
speech recognition.  For a long time that is going to rely on relatively 
clean audio.  Even if automated translation in noise becomes possible, 
with the amount of noise, etc., on an amateur radio circuit, the 
additional degradation in going from digital to analogue and back is 
likely to be negligible.


There is also a fundamental problem with machine translation in that the 
solution for the translation will not stabilise until the end of 
sentence, or later.  Whilst a human also needs to reach this point for 
full understanding, they will have part processed the speech before they 
get there.  In the general case, the machine translator cannot even 
start passing the translation on to the human until it reaches this 
point, so there will always be a significant extra processing delay, 
compared with understanding the language, directly.


I would also expect any software or hardware that comes onto the market 
to have been designed for use with at least the telephone bandwidth of 
300-3.4kHz, not the narrower bandwidth used for SSB radio.  Even 
telephone bandwidth is not enough to accurately recognize sibilants (s, 
sh, h, etc.).


The main case where direct digital is useful is for digital mode, where 
phase errors, which have no impact on speech recognition, may be 
significant.


On 30/03/17 19:20, Steve Sergeant wrote:


How abut signal processing operations that
are beyond the DSP capability in the radio? How about some
not-so-distant future when spoken language translation might be possible?


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Re: [Elecraft] K2 main encoder wanted

[David Woolley]

WD40 is a preservative, not a lubricant.  It will act as a penetrating 
oil, to free seized parts, but for a longer term solution you want to 
look at sewing machine or hair clipper oil.


On 25/03/17 20:57, Bob G3PJT wrote:


I have managed to get the encoder turning reasonable freely. I put a
very small amout of WD40 on the shaft where it enters the housing bush.



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Re: [Elecraft] Dimmable LED desk lamp

[David Woolley]

The light from white "LEDs" is a mixture of a fairly narrow, blue, peak, 
direct from the LED, and a broad, low, yellow one from the phosphor. 
The fact that they don't excite the phosphor with UV is one of their 
advantages, when compared with CFLs (where the actual physics is also 
pretty much constant current driven).


More expensive ones, will have a red LED as well to give better 
rendition of reds.


A lot of the visible light IS from the LED.

On 07/01/17 12:55, Charlie T, K3ICH wrote:

The actual light is emitted NOT by the LED itself, but a phosphor coating
inside the LED which is excited by the LED's output.   Dirt-cheap hand


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Re: [Elecraft] Dimmable LED desk lamp for operating position recommendation needed

[David Woolley]

There will be a switching converter on any quality make of LED lighting. 
 The only way you avoid it is if they use a simple series dropper 
resistor, which is not energy efficient.


LEDs are constant current devices, so there is no such thing as a 12V 
LED (an LED with a 12V forward voltage drop would be well into the far 
ultraviolet, and would still need current regulation).


Professional installations would use a switching constant current supply 
(typically called a driver).  Those for amateurs and the average 
building contractor would mimic tungsten bulbs by having a constant 
current switching regulator in each bulb.


Some cheap mains operated lamps use capacitive droppers followed by 
rectifier and resistive current limiter.  They are the type likely to be 
sold in one dollar stores, or on Ebay.

#
On 06/01/17 11:50, Marc Veeneman wrote:

\


On Jan 6, 2017, at 2:00 AM, Peter D. Vouvounas  wrote:

I presume some of you have been through a selection process to find a usable
dimmable LED desk lamp with articulating arm that does not create RFI back
into your Flex on HF.




I mounted (dual side adhesive tape) an LED strip to the underside of an 
equipment shelf.  The strip came with a 12v switcher that I ignored.  I use my 
12 volt supply.  The strip was, I think, 24 inches long and has a dimmer that 
can be inserted in the power lead.  No RFI.  Plenty bright.  Mine came from 
Amazon but there are many to choose from these days; you can even select color 
temperature when you order.



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Re: [Elecraft] [K3] The Way We Rank Receivers (long)

[David Woolley]

The main commercial interests in subjective audio noise reduction, 
particularly for speech, are probably the hearing aid industry.


It is subjective because noise reduction only really removes noise that 
isn't interfering.  That is still useful, as whilst the human brain can 
also do that, it gets tired in the process.


On 25/10/16 16:13, brian wrote:

This would be tough since the world of RFI sources is huge.  It would
take some real effort to quantify the world of noise sources and their
signatures and then find some algorithms to deal with them.  Impossible?
The world of big data isn't so big any more. Such an catalog might be
doable.  Algorithms are another issue.  My hope is that NR/NB could be
made adaptive to recognize the signature(s) and generate appropriate
algorithms on the fly.

There are a lot of smart people out there who could perhaps address
these issues.  Unfortunately commercial interests have to see some
payoff.  They haven't as of yet.  The fact that AM broadcasters are
being burned by RFI and becoming proactive is a plus.


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Re: [Elecraft] Mag Loop

[David Woolley]

You can put away the tin foil!  The lines of force arriving thousands of 
miles away are not going through your loop; they are closed loops that 
are no more than half a wavelength across in the direction of travel. 
That's the difference between near and far fields.


On the other hand, that thought may make the tin foil more desirable!

On 21/10/16 00:11, Fred Jensen wrote:


I worked a couple of DL's using my K2 @ 5W and AlexLoop from a summit in
SE New Mexico on 15.  Kind of sobering to realize that all the lines of
force going everywhere several thousand miles away come together through
the center of the little loop directly over my head, and a tinfoil hat
won't help.


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Re: [Elecraft] K3/K3S noise blanker performance greatly enhanced (at my QTH) -- need testers

[David Woolley]

Noise reduction is a difficult problem and hearing aid manufacturers 
have been trying to solve it for the last couple of decades.


One important point to note is that noise reduction is normally aimed at 
reducing subjective noise and therefore reducing fatigue.  Generally 
what you are doing is actually recognising signal, then suppressing 
those frequencies that are not conveying the signal.  The noise on the 
same frequencies as important parts of the signal still gets through.


You cannot remove noise unless you have first identified the signal, so 
you cannot remove the noise that is masking an unknown signal.


The simplest noise reduction is a narrow band CW filter!  The ultimate 
noise reduction for CW would be to decode the signal, and regenerate it, 
but that is currently only possible for signals that are already clean 
an well formed.


Decode and  recreate might be the ultimate solution for hearing aids, as 
well.


--
David Woolley
Owner K2 06123

On 06/02/16 03:35, drewko wrote:

I'm glad that noise solutions are being investigated. I think advances
in NR/NB would be of more importance to many hams than close-in dynamic
range, however useful the improvement in those attention-getting figures
are. On a day to day basis noise is the top culprit for many of us.


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Re: [Elecraft] Long RS232 Runs - RS422

[David Woolley]

The +/- 3 volts levels are requirements on the driver, not the receiver. 
 In practice, receivers have quite a small hysteresis, and the 
threshold points are set to meet the requirements of a type 1 interface 
as defined in section 7 of ITU-T V.28.  Whilst the specified purpose of 
this is that a powered down or open circuit condition should result in 
defined states for, particularly control signals (off), in practice it 
means that real world receivers will also handle high speed signals 
which are strictly positive.


Consequently levels of +5 and 0 volts will, in most normal cases, work, 
although they are out of specification.


ITU-T V.28 is generally aligned with the electrical characteristics of 
EIA232, but has the advantage that the document is available for free 
download.


--
David Woolley
Owner K2 06123

On 21/01/16 20:03, Cliff Frescura wrote:

RS-232 use +3 to +15VDC and -3 to -15VDC for signaling levels, thus -5 and +5 
will work too, but *not* 0VDC and +5VDC




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Re: [Elecraft] K3S RS232 "Y" Connector causing port conflict

[David Woolley]

Actually, the large mainframe would have been a DTE as well.  It is the 
modem that is the DCE.  The specification is really one for connecting 
things to modems.


Initially PCs used 25 pin connectors and they were fairly rare in using 
them with the correct gender, male (as defined by the pins) for DTE and 
female for DCE.  Even after the move to 9 pins, they continued to use 
this convention.  Therefore, if you have a device that has a male 
connector, you can be pretty sure it is configured as a DTE.  A female 
connector, unfortunately, is not a guarantee of the converse, and the 
K2, at least, appears to be non-compliant.  It looks like the K3 has the 
same non-compliance.


--
David Woolley
Owner K2 06123


On 14/12/15 23:08, Don Wilhelm wrote:


AFAIK the IBM PC was the first to use the DE-9 connector for the serial
port connector, and they initially envisioned the PC being used as a
terminal device connected to a large mainframe - so the mix-up began
there - thus the PC is a DTE device, and when things are run from a PC,
the signals are "backwards".


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Re: [Elecraft] Receivers?

[David Woolley]

I don't think these descriptions are accurate, particularly the K2 
versus K3 one.


The K2 is a fairly conventional, single conversion, analogue design.  As 
stated, it uses the crystal filter for primary selectivity.  It 
typically has up to two crystal filter options, one hard wired, and the 
other as an integral part of the SSB adapter.  The hard wired one is 
adjustable, and the SSB one is fixed.  The filters are constructed by 
the final assembler, from individual crystals.  Although there is a DSP 
option, it works purely on the audio.


The K3 and K3X are software defined radios (SDRs) of the non-direct 
sampling variety.  I use SDR in the technical sense, not in the amateur 
radio community sense; the latter requires the digital processing to be 
performed on a PC.  This means they have an analogue front end with at 
least one analogue mixer, but the final processing is done digitally.


The K3 has a double conversion superhet architecture, with an HF first 
IF and an extremely low second one.  There is a selectable crystal 
filter (using commercial sub-assemblies) in the first IF, which provides 
coarse selectivity.  The final IF processing is digital.  There is a 
quadrature path starting from the second mixer, analogue at that stage. 
 Combined with digital processing, this creates an analogue of a 
phasing design receiver to suppress the final IF image, rather than the 
audio image.  As the signal continues in quadrature, the digital 
processing may also act analogously to a phasing receiver to do the 
final conversion and audio image stripping, but it may be that the 
internal logic is more complex than that - the fine details are a trade 
secret, although they may or may not have release information about that 
part of it.


The K3 also does digital processing on the recovered audio, but this is 
done within the same digital processor as the final IF processing.


The K3X, for CW at least, implements a hybrid analogue/SDR direct 
conversion, phasing design.  For SSB it may do the same, but it is also 
possible that it actually implements a final passband centre at 0Hz, and 
then does a final frequency shift to move the centre of the passband to 
the correct audio frequency (i.e. they could have implemented it as a 
single conversion architecture).  Selectivity is provided entirely by 
digital processing.


For both the K2 and K3, first mixer image rejection is provided by a 
combination of band pass filters, optimised for each band, and a low 
pass filter, also optimised for the band.  For the KX3, the image is the 
one removed by the phasing, although there is also analogue band and low 
pass filtering - I'm not sure whether this is switched, or there is a 
single, compromise, filter.


Block diagrams for all three are fairly easy to find.  I have the K2, so 
did that from memory, but the K3 one is at 
<http://www.qsl.net/wb4kdi/Elecraft/K3/K3_Block.png> and the KX3 at 
<http://www.elecraft.com/manual/KX3%20Manual%20Block%20Diagram.pdf>. 
There are likely other places, including a better K3 image.


--
David Woolley
Owner K2 06123

On 11/12/15 21:40, Ron D'Eau Claire wrote:

The K3 and K2 and conventional superhetrodyne formats with an Intermediate
Frequency in the H.F. range and crystal filters to set the passband. The K2
has an adjustable crystal filter and the K3 uses fixed crystal filter
bandwidths. The basic K2 bandwidth is established by the crystal filter
while the K3 adds an adjustable DSP filter after the crystal filter. (The K2
has an optional audio DSP for enhanced filtering.)


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